EIF2AK3 and craniosynostosis: The lack of phenotype in these overexpressing mutants suggests that, although pERK is upregulated in both Fgfr2cC342Y and R26RFgfr2c;βact, only Fgfr2cC342Y sutures show increased differentiation as revealed by increased levels of ALP, hence the craniosynostosis phenotype.